1. Field of the Invention
The present invention relates to a process for producing 3,7,11,15-tetramethylhexadeca-2E,6E,10E, 14-tetraenol (hereinafter referred to simply as "geranylgeraniol").
The geranylgeraniol obtained by the present invention are useful as starting materials for producing vitamin K2, tocotrienol and so on.
2. Related Art of the Invention
Known processes for producing geranylgeraniol include, for example, (1) a process wherein trialkylphosphonoacetates are reacted with farnesylacetone, followed by reduction of the resultant compound with aluminium hydride [SYNLETT 783 (1993)], and (2) a process wherein geranyl p-toluenesulfonate is reacted with 8-bromogeranyl acetate using n-butyl lithium, followed by de-sulfonation with metallic lithium and amines (Japanese Patent Laid-open No. Sho 54-55506).
The geranylgeraniol obtained by these processes includes geometrical isomers wherein one or more of the carbon-carbon double bonds in the molecule are in cis form. Therefore, it is necessary to purify the mixture through precise distillation or column chromatography in order to obtain pure geranylgeraniol, whose carbon-carbon double bonds are all in trans form. However, geranylgeraniol has high boiling point and an ally alcohol structure which is thermally unstable, so that the precise distillation of geranylgeraniol is extremely difficult. On the other hand, the purification of geranylgeraniol through column chromatography needs not only large amounts of solvents and packing materials such as silica gel, but also the preparation of a developing solvent and successive analysis of eluted fractions in relation to time. In the latter case, it is necessary that a desired fraction or fractions should be collected based on the analysis, after which the solvent has to be removed. Thus, the purification of geranylgeraniol with column chromatography requires very complicated operations, and are not suitable for industrial applications.